The Chinese state news media portrayed the demonstrations as fairly small, each involving fewer than 200 people, and not extending to inland provinces. But photographs posted on Sina Weibo, the country’s most widely used microblogging service, suggested that the crowds had been far larger. In one photo said to be from the southwestern city of Chengdu, deep in China’s interior, the number of protesters appeared to be tens of thousands.

“Defend the Diaoyu Islands to the death,” one banner said. Another said, “Even if China is covered with graves, we must kill all Japanese.”

Another photograph showed a handwritten sign taped to the entrance of Suning, a popular electronics store, telling customers it was no longer selling Japanese products.

Some protests appear to have turned violent. According to several postings, demonstrators on Sunday attacked sushi restaurants or other businesses perceived to have a Japanese connection. Several photographs said to be from Shenzhen, across the border from Hong Kong, showed what appeared to be damaged or overturned cars — most of them Japanese models — as well as several police vehicles.

Tensions on the Diaoyu Islands (Senkaku Islands in Japanese) have escalated since April, when the governor of Tokyo announced plans for the city to purchase them. Despite warnings from Chinese state media telling the Japanese not to interfere with the boat from Hong Kong, the Japanese Coast Guard detained 14 of the activists before allowing them to return to Hong Kong on Saturday. The China Daily then reported that 10 Japanese activists landed on the Diaoyu Islands on Sunday morning, despite not having approval from the Japanese government. They are believed to be part of a larger fleet of 150 Japanese activists and 21 vessels that planned to hold a ceremony in the nearby waters for those who died in World War II.

Sunday’s landing, along with a barrage of other provocations, has poisoned the atmosphere of the Sino-Japanese relations and constituted another setback for both countries’ efforts to further their political and economic ties.

The Japanese rightists should immediately stop any action that undermines Chinese territorial sovereignty and be barred from fuelling the tension between the two neighbors.

To this end, the Japanese government should act with great responsibility and proceed from the overall interests of the Sino-Japanese relations to seek a peaceful settlement of any disputes.

Chinese protestors gathered in dozens of cities, in some cases vandalising Japanese-made cars and retail outlets. About 1,000 people marched in the southern city of Shenzhen, overturning a Japanese-made police vehicle and attacking a Japanese restaurant, according to Xinhua, the Chinese state news agency.

In the western city of Chengdu, a branch of Uniqlo, the Japanese clothing store, had to close due to the protests. Demonstrations were also reported in a dozen other Chinese cities including Shanghai, Guangzhou, Xian, Jinan and Qingdao. In Beijing, a few protesters appeared outside the Japanese embassy on Sunday morning amid heightened security, but there was no other sign of unrest in the capital.